1. Field of the Invention
The present invention relates to an ink jet recorder, such as an ink jet printer having a purging apparatus for sucking ink from a ink jet head, and a purging method and recording method for the ink jet printer.
2. Description of Related Art
Ink jet printers are known generally as ink jet recorders for recording on recording media, such as sheets of paper, by ejecting ink onto them.
FIG. 13 of the accompanying drawings shows part of a conventional ink jet printer, which includes a recording head unit P3 having a recording head P2. The head P2 has four ejection nozzles P4, each of which has ejection holes (not shown) opening in its front surface P5. Four ink cartridges P1 containing link are mounted replaceably on the head unit P3, and each connected to one of the nozzles P4. After each cartridge P1 is replaced with a new one, ink is supplied from the new cartridge to the head P2, and can be ejected from the associated nozzle P4.
While the printer is used, ink may be sucked from the nozzle surfaces P5 to purge the nozzles. The purging may be started manually by the user operating a switch on the printer, or automatically if a predetermined condition is satisfied.
The purging is performed to prevent the defective ejection of ink which may be caused if the ink in or on the recording head P2 dries, or if air bubbles are produced in the ink, or if droplets of ink stick to the nozzle surfaces P5. Specifically, the purging of each nozzle P4 involves covering its nozzle surface P5 with a suction cap P6, and then developing negative pressure in the cap P6 by means of a suction pump (not shown), in order to suck ink from the head P2 through the cap P6 and discharge the sucked ink outside.
It is not avoidable that, when each cartridge P1 is replaced with a new one, air enters the flow passage between the new cartridge P1 and the recording head P2. Therefore, after the new cartridge P1 is substituted, the purging is repeated consecutively as initial purging to remove the air from the passage and introduce new ink into the head P2.
If a recording command is input in the printer, the ejecting function of the printer is recovered by purging depending on the period (days) of nonuse of the printer, and immediately thereafter the printer starts printing. Just after the purging, very small air bubbles may be produced in the ink in the recording head P2. For example, air bubbles may be produced by the rapid flow of ink due to the purging. On the other hand, the purging may cause ink to bubble in the suction cap P6. In this case, when the cap P6 is separated from the nozzle surface P5 of the purged nozzle P4, the bubbly ink in the cap is forced into the nozzle by the negative pressure acting from the inner side of the nozzle. If air bubbles thus remain in the ink passages, the bubbles may absorb part of the ejection pressure and block part of the passages when ink is ejected. This impedes or hinders the ejection, and lowers the recording quality.
If quite a long time has passed after the last recording, two or more cycles of purging may be performed to improve the ejection of ink. In particular, the purging is repeated consecutively a plurality of times as the initial purging for introducing new ink into the recording head P2 after each cartridge P1 is replaced. After such a series of purges, air bubbles may remain in the purged nozzle P4 or the associated ink flow passage in the head P2. The ink flow velocity is lower toward the wall of the passage, and it is therefore difficult to remove the bubbles near the wall. Consequently, even if the purging causes ink to flow, air bubbles are liable to collect near the passage wall. Because the purging is repeated consecutively, the bubbles near the passage wall grow larger. This is considerable in particular at the corners of the passage, lowering the recording quality.
It is an object of the invention to provide an ink jet recorder which can perform good recording without its ejecting characteristic worsening even after purging.
It is another object of the invention to provide an ink jet recorder including a recording head having a plurality of ejection nozzles which can be purged individually, the recorder being able to cause the air bubbles produced in the head by purging to vanish effectively, and able to shorten the standby time.
It is still another object of the invention to provide a recording method for enabling the air bubbles produced in the recording head of an ink jet recorder by purging to vanish effectively.
It is a further object of the invention to provide a purging method which enables the air bubbles produced in the recording head of an ink jet recorder by purging to vanish effectively, and which can shorten the standby time. The head has a plurality of ejection nozzles which can be purged individually.
In accordance with a first aspect of the invention, an ink jet recorder is provided. The recorder includes a recording head having an ejection nozzle for ejecting ink onto a recording medium. The recorder also includes a purging apparatus for purging the nozzle to improve the ejection of ink from the nozzle. The recorder further includes a judging device and an authorizing device. If a command for operating the head is input in the recorder, the judging device judges whether a first time period has passed or not after the last purging by the purging apparatus. If the judging device judges that the first period has passed, the authorizing device authorizes the operation of the head. Thereby, the recorder performs recording, not just after the nozzle is purged, but when the first time period has passed after the purging. This period is sufficient for most of the air bubbles produced by the purging to vanish naturally. This eliminates air bubbles from the ink in the recording head, improving the ejecting characteristic. It is therefore possible to secure high recording quality.
The ink jet recorder may further include a purge controller for controlling the purging apparatus. The controller may make the purging apparatus perform purging before the recording head starts the recording authorized by the authorizing device. If the passage of time after the first time period is considerably short, the controller may control the purging apparatus in such a manner that no purging is performed. If the passage of time after this period is considerably long, recording may be started after purging is performed as the need arises. Thereby, the head is restored from the dryness of ink caused after the last purging and/or the production of air bubbles also caused after the last purging in the ink in the head. If this purging is performed, it is possible to cause the bubbles produced by the purging to vanish, by controlling the purging apparatus in such a manner that this apparatus waits a predetermined time after the purging and before the head starts recording.
The recording head may have a plurality of ejection nozzles in place of the single nozzle. In this case, the purging apparatus can purge each nozzle in accordance with an input command. When two or more of the nozzles are purged, the purge controller may make each of the two or more nozzles purged once in order and at least once again in order. After each of these nozzles is purged once and before it is purged at least once again, it may wait a predetermined time so that the air bubbles produced by the purging may vanish. After the predetermined time passes, similar purging may be repeated two or more times for the two or more nozzles. By purging the nozzles in such order, it is possible to effectively secure the time which the bubbles produced by purging take to vanish. The first time period may be one minute so that the bubbles produced by the last purging vanish securely.
The recorder may further include a timer for clocking the second time period after the last purging. If a command for operating the recording head is input in the recorder, the purge controller may control the purging by the purging apparatus, depending on the second period clocked by the timer, and the authorizing device may authorize the recording by the head when the first time period has passed after the purging controlled depending on the second period. This makes it possible to keep the head in good condition by controlling the purging depending on the second period, during which ink may dry and/or air bubbles may be produced in the ink in the head.
In accordance with a second aspect of the invention, another ink jet recorder is provided. The recorder includes a recording head having a plurality of ejection nozzles for ejecting ink onto a recording medium. The recorder also includes a purging apparatus which can purge the nozzles one after one to improve the ejection of ink from the nozzles. The recorder further includes a determining device, a purge controller and an authorizing device. The determining device determines the time having passed after the last purging. If there is a command for operating the head, the purge controller controls the purging depending on the length of the time determined by the determining device. The authorizing device can authorize the operation of the head, after or without purging, in accordance with the determination by the determining device. When two or more of the nozzles are purged, the controller makes the two or more nozzles purged once in order and at least once again in order. As stated above, the determining device determines the time which has passed after the last purging. If a very long time has not passed after the last purging, no further purging may be performed. If a long time has passed, additional purging may be performed. This controls the purging depending on the period during which ink may dry and/or air bubbles may be produced in the ink in the recording head. It is therefore possible to keep the head in good condition. After one of the nozzles is purged and before it is purged again, another may be purged. This shortens the standby time before recording, and prevents the bubbles from growing after purging.
In accordance with a third aspect of the invention, a still another ink jet recorder is provided. The recorder includes a recording head having a plurality of ejection nozzles for ejecting ink onto a recording medium. The recorder also includes a purging apparatus which can purge the nozzles one after one to improve the ejection of ink from the nozzles. The recorder further includes a purge controller for controlling the purging by the purging apparatus in such a manner that, when two or more of the nozzles are purged, they are purged once in order and at least once again in order. The method for purging nozzles of the conventional recorder a predetermined number of times includes purging one of the nozzles consecutively the predetermined number of times, and thereafter purging another consecutively the same number of times.
When two or more nozzles of the recorder according to the third aspect of the invention are purged, they are purged once in order and once again in order, and thereafter a series of similar purges may be repeated for them. Thus, after one of the nozzles is purged and before it is purged again, another is purged. It is therefore possible to lengthen the time interval between purges for each nozzle in comparison with the conventional recorder. Produced air bubbles can vanish during the lengthened interval. It is consequently possible to shorten the standby time, enabling the recording to start speedily. Because purging is performed again after air bubbles produced by the last purging vanish once, it is possible to prevent the bubbles from growing during the succeeding purging. In this case, the purge controller may make two or more of the nozzles purged once in order, then wait a predetermined time, and thereafter purged at least once again in order. By thus interposing the waiting time further, it is possible to prevent the bubbles more effectively from growing during the next purging.
In accordance with a fourth aspect of the invention, a yet another ink jet recorder is provided. The recorder includes a recording head having an ejection nozzle for ejecting ink onto a recording medium. The recorder also includes a purging apparatus for purging the nozzle. The recorder further includes a controller for controlling the purging apparatus in such a manner that the apparatus repeats first purging for the nozzle a first predetermined number of times, then halts until the predetermined time has passed which the air bubbles in the ink in the head take to vanish, and thereafter performs second purging for the nozzle a second predetermined number of times.
If a long time has passed after the last use of this recorder, it may be necessary to purge the ejection nozzle two or more times. On the other hand, in order to introduce ink initially to the recording head, it may also be necessary to purge the nozzle two or more times. The air bubbles produced by the first purging may stick to the walls and/or corners of the ink flow passage. In this case, by halting the purging between the first purging and the second purging to secure the time which the bubbles take to vanish, the bubbles can vanish during the halt. Because the second purging is performed thereafter, it is possible to inhibit the bubbles from growing at the next purging, and remove the bubbles which the first purging has not been able to remove. As a result, it is possible to secure high recording quality which overcomes the hindrance due to the bubbles.
This recorder may further include an ink supply for supplying the recording head with ink. The predetermined number of repetitions of the first purging may be necessary for introducing ink from the supply up to the front end of the ejection nozzle. In this case, ink reaches the front end of the nozzle before the halt. The strong surface tension of the ink at the nozzle end keeps ink from being drawn back toward the supply.
In accordance with a fifth aspect of the invention, a further ink jet recorder is provided. The recorder includes a recording head having an ejection nozzle for ejecting ink onto a recording medium to record on the medium. The head can be supplied with ink from an ink cartridge. The recorder also includes a suction cap for contact with the nozzle surface of the nozzle, and a suction pump for sucking ink out of the cartridge from the ejection side of the nozzle through the cap. The recorder further includes a purge controller for controlling the purging of the nozzle by the cap and the pump.
After the cartridge is replaced with a new one, the controller makes the nozzle purged the number of times which is necessary for introducing ink from the new cartridge up to the front end of the nozzle. Then, the controller halts the purging until the time passes which the air bubbles in the introduced ink take to vanish. Thereafter, the controller makes the nozzle purged a predetermined number of times. When ink is introduced initially from the substituted new cartridge into the recording head, air bubbles may enter the head together with the ink, but can vanish.
This recorder might include two or more nozzles for ejecting various color inks, and ink cartridges each connected to one of the nozzles.
In accordance with a sixth aspect of the invention, a further ink jet recorder is provided. The recorder includes a recording head having at least one ejection nozzle for ejecting ink onto a recording medium. The recorder also includes a purging apparatus for recovering the ejection of ink from the nozzle. The recorder further includes a timer and a controller. The timer clocks the time having passed after the last purging by the purging apparatus. The controller controls the head and the purging apparatus. If the clocked time exceeds a predetermined time period, the controller starts the head ejecting ink.
In accordance with a seventh aspect of the invention, a recording method of an ink jet recorder is provided. The recorder includes a recording head having an ejection nozzle. The recorder also includes a purging apparatus for purging the nozzle. The method includes the steps of:
clocking the time which has passed after the last purging by the purging apparatus;
judging whether the clocked time exceeds a predetermined time period or not, before the recording by the head;
starting the recording by the head if it is judged that the clocked time exceeds the period; and waiting for the recording until the clocked time exceed the period if it is judged that the clocked time does not exceed the period.
This recording method makes it possible to avoid the hindrance due to the air bubbles produced by purging, and is therefore very useful for an ink jet printer fitted with an apparatus for purging the nozzle of the recording head.
The recording method may also include the step of purging the nozzle before the recording by the recording head if it is judged that the clocked time exceeds the predetermined time period.
In accordance with an eighth aspect of the invention, a purging method of an ink jet recorder is provided. The recorder includes a recording head having a plurality of nozzles for ejecting different color inks. The recorder also includes a purging apparatus for purging the nozzles one by one. The method includes the steps of purging the nozzles once in order, and thereafter purging the purged nozzles at least once again in order.
When the nozzles are purged, this purging method makes it possible to effectively remove the air bubbles produced by the last purging, and to shorten the standby time before recording. Therefore, the method is very effective in the purge control of an ink jet printer or the like.